The subjects in this presentation listened to and compared real sound fields to artificial-head
recordings of the same sound field. This study was designed to evaluate comparative localization
performances of artificial heads. The results of listeners' localization performance tests, when
comparing artificial-head recordings to those of the real sound fields, resulted in an increased
number of errors. The results obtained when using some of the artificial heads in this study also
showed an increase in confusion of directionality perception outside the median plane. The overall
conclusion indicated the need for an improved artificial-head design.

Synthesizing piano sound is a difficult task because it is subject to spectral changes during its long
decay. Group synthesis, a special case of wavetable synthesis, has been adapted by the authors to
efficiently model piano sounds. It requires about one half the data allocation required by additive
synthesis. This solution is computationally about twice as fast as additive synthesis. Plucked strings,
percussive mallet sounds, and bell tones are good future test cases for this synthesis model.

The noise performance of an amplifier's input stage consisting of a number of parallel connected
semiconductor devices is examined. The resultant equivalent input voltage noise is measured while
keeping the bias current constant and varying the number of input devices. The result is then
compared to the noise while holding the bias current per device constant. The findings of this study
contribute significantly to the understanding of low-noise amplifier input system designs.

Acoustic problems attendant to Russian theaters, which were built in classical style, having
horseshoe-shaped floor plans with several rows of balconies, were investigated. Reverberation times
of these old halls were measured under varying conditions and the results analyzed. The goal of this
investigation was to make suggestions for renovating the old halls to improve their acoustical
performance. This study also provides acoustic guidelines for the design of future performance halls.